63 lines
1.5 KiB
Perl
63 lines
1.5 KiB
Perl
#!/usr/bin/env perl
|
|
|
|
use strict;
|
|
use warnings;
|
|
|
|
my @wordgrid = ();
|
|
while (<>) {
|
|
next if /^\s*$/;
|
|
chomp;
|
|
push @wordgrid, [ split //, $_ ];
|
|
}
|
|
|
|
my @directions = ();
|
|
for my $a (-1 .. 1) {
|
|
for my $b (-1 .. 1) {
|
|
next if ($a == 0 && $b == 0);
|
|
push @directions, [map { [$a * $_, $b * $_ ] } (0 .. 3)];
|
|
}
|
|
}
|
|
|
|
my @diagonal = ([-1, -1], [0, 0], [1, 1]);
|
|
my @otherdiagonal = ([1, -1], [0, 0], [-1, 1]);
|
|
|
|
my $xmas_count = 0;
|
|
my $mas_cross_count = 0;
|
|
for my $y (0 .. $#wordgrid) {
|
|
for my $x (0 .. $#{$wordgrid[$y]}) {
|
|
$xmas_count += grep { search_letters([$x, $y], $_, [split //, "XMAS"])} @directions;
|
|
$mas_cross_count++ if search_mas_cross([ $x, $y ]);
|
|
}
|
|
}
|
|
|
|
print "Part 1: ", $xmas_count, "\n";
|
|
print "Part 2: ", $mas_cross_count, "\n";
|
|
|
|
sub search_letters {
|
|
my ($start, $offsets, $letters) = @_;
|
|
|
|
for my $i (0 .. $#{$letters}) {
|
|
my $cord = [$start->[0] + $offsets->[$i]->[0], $start->[1] + $offsets->[$i]->[1]];
|
|
return 0 if (
|
|
$cord->[1] < 0 || $cord->[1] > $#wordgrid ||
|
|
$cord->[0] < 0 || $cord->[0] > $#{$wordgrid[$cord->[1]]}
|
|
);
|
|
return 0 if $wordgrid[$cord->[1]][$cord->[0]] ne $letters->[$i];
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
sub search_mas_cross {
|
|
my $start = shift;
|
|
my @mas = split //, "MAS";
|
|
return 0 if $wordgrid[$start->[1]][$start->[0]] ne "A";
|
|
return 0 if (
|
|
!search_letters($start, \@diagonal, \@mas) &&
|
|
!search_letters($start, [reverse @diagonal], \@mas)
|
|
);
|
|
return 0 if (
|
|
!search_letters($start, \@otherdiagonal, \@mas) &&
|
|
!search_letters($start, [reverse @otherdiagonal], \@mas)
|
|
);
|
|
return 1;
|
|
}
|